Impact of selenium fertilization on the activity of detoxifying enzymes of H2O2 in bean plants

Selenium (Se) is an essential element for many organisms, although in high concentrations it may become toxic, leading to the generation of reactive oxygen species (ROS). In this study, bean plants received different application rates of Se (0, 10, 20, 40, 80, and 160 mu M) in the form of selenite and selenate to evaluate the activity of the detoxifying enzymes of H2O2. The results indicated that the activity of these enzymes in bean plants depended on the chemical form of Se: selenite at rates of 20 mu M or greater diminished biomass and yield, increasing the activity of superoxide dismutase (SOD). Even when catalase (CAT) activity also increased, it appeared that it was efficient at detoxifying H2O2 in the presence of Se, given also the rise in H2O2 production. Also, selenate diminished yield up to a rate of 160 M and increased the activity of the enzyme GSH-Px, which reached its maximum activity at 160 mu M, and thus proved less toxic than selenite.